New 370 build, cranks, no fire
10-29-2018, 07:30 PM
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New 370 build, cranks, no fire Hey Guys, Been a long time lurker, this is my first post, I need help and I can usually find the answer here but this one has just been evading me.
Vehicle- 2005 Silverado Z71, 5.3 w/4L60E and 4wd
Pulled the 5.3 for a 370 I built, 2003 LQ4- K1 crank, rods, wiseco pistons, TSP 212/218 low lift cam, TBSS intake, LS3 throttle body w/ x link, stock 5.3 injectors
Did the swap, all new grounds, connectors are clean and hooked up correctly.
Have not been able to get it to start. It cranks fine, compression is good, leakdown is good, used a noid light- all injectors are good, used spark tester- all coils are good.
It pushes the air/fuel mixture back up through the intake and out the throttle body and stars a nice little fire in the intake manifold.
Any ideas on what the issue could be? I used brand new crank and cam sensor- swapped them out for the original ones (that I know work)- no change. I verified again that the cam is installed correctly and the valves are cycling as they should. Can not figure out for the life of me what the issue is, it sounds like timing but this isn't an SBC. Any input would be appreciated
Vehicle- 2005 Silverado Z71, 5.3 w/4L60E and 4wd
Pulled the 5.3 for a 370 I built, 2003 LQ4- K1 crank, rods, wiseco pistons, TSP 212/218 low lift cam, TBSS intake, LS3 throttle body w/ x link, stock 5.3 injectors
Did the swap, all new grounds, connectors are clean and hooked up correctly.
Have not been able to get it to start. It cranks fine, compression is good, leakdown is good, used a noid light- all injectors are good, used spark tester- all coils are good.
It pushes the air/fuel mixture back up through the intake and out the throttle body and stars a nice little fire in the intake manifold.
Any ideas on what the issue could be? I used brand new crank and cam sensor- swapped them out for the original ones (that I know work)- no change. I verified again that the cam is installed correctly and the valves are cycling as they should. Can not figure out for the life of me what the issue is, it sounds like timing but this isn't an SBC. Any input would be appreciated
10-29-2018, 07:45 PM
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10-29-2018, 09:11 PM
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Timing can be off but like your tuner suggested, it would be mechanical. Your symptoms do sound like a timing issue to me too. you’re 100% sure the cam dot is at 6 o’clock and the crank dot is at 12 o’clock? Is your cam sensor on the engine block rear or the timing cover? Also are you running a 24x or 58x crank reluctor and does it match what was originally on the engine?
10-30-2018, 11:28 AM
#6
^^ I’m thinking that would be tough to do on an engine that is assembled and installed in the truck. My comment was more based around the OP verifying the crank reluctors were the same when he assembled the engine. I do know the tooth count could be checked by removing the KPS and looking in the hole. Pretty easy to check that on an assembled engine. A borescope would make it a lot easier if the engine is installed in the vehicle. Can’t say for sure that a mismatch tooth count would case this symptom but it’s worth verifying considering the mismatch engine model years.
10-30-2018, 03:42 PM
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IDK why but my last post isn't showing up.
I'm going to pull out the degree wheel and degree the cam the right way.
'05 silverado had 24x reluctor, '03 LQ4 has 24x reluctor, I bought a K1 crank with 24x reluctor
I'm going to pull out the degree wheel and degree the cam the right way.
'05 silverado had 24x reluctor, '03 LQ4 has 24x reluctor, I bought a K1 crank with 24x reluctor
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10-30-2018, 06:20 PM
#8
Have you verified that you are getting a crank position signal to PCM? When cranking, does the tach needle bounce up off zero? If the needle does not move while cranking, check CPK (crank position sensor) to be sure that it is plugged in. It's easy to knock it off, or break it, when putting the starter in. If you had HP Tuners you could log various channels while attempting to start it and it would give you some very good data.
11-01-2018, 08:06 PM
#10
Cam is off timing or the coil wiring to the coils was mixed up or the coil brackets got flipped from one side to the other.
One way or another ignition or cam is out of time, that's the only thing that makes them sneeze like that, unless the intake valves are hanging open. If you had the coils off the brackets and the wiring the wiring could be off (wrong firing order), I've had to fight that one before. I haven't had it happen but from what I hear if you put the coil set from one side on the other side it will be out of time, I haven't verified if that's a real deal or not.
Reluctor could be on wrong but not very likely, or the wrong tooth count but sounds like you verified that already.
One way or another ignition or cam is out of time, that's the only thing that makes them sneeze like that, unless the intake valves are hanging open. If you had the coils off the brackets and the wiring the wiring could be off (wrong firing order), I've had to fight that one before. I haven't had it happen but from what I hear if you put the coil set from one side on the other side it will be out of time, I haven't verified if that's a real deal or not.
Reluctor could be on wrong but not very likely, or the wrong tooth count but sounds like you verified that already.
11-02-2018, 09:07 AM
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Cam is off timing or the coil wiring to the coils was mixed up or the coil brackets got flipped from one side to the other.
One way or another ignition or cam is out of time, that's the only thing that makes them sneeze like that, unless the intake valves are hanging open. If you had the coils off the brackets and the wiring the wiring could be off (wrong firing order), I've had to fight that one before. I haven't had it happen but from what I hear if you put the coil set from one side on the other side it will be out of time, I haven't verified if that's a real deal or not.
Reluctor could be on wrong but not very likely, or the wrong tooth count but sounds like you verified that already.
One way or another ignition or cam is out of time, that's the only thing that makes them sneeze like that, unless the intake valves are hanging open. If you had the coils off the brackets and the wiring the wiring could be off (wrong firing order), I've had to fight that one before. I haven't had it happen but from what I hear if you put the coil set from one side on the other side it will be out of time, I haven't verified if that's a real deal or not.
Reluctor could be on wrong but not very likely, or the wrong tooth count but sounds like you verified that already.
I've heard the cloyes adjustable timing set I have, has had previous issues where the crank dots are incorrect. I am pulling out the degree wheel this weekend and will verify cam timing. I'll update this post afterwards
11-02-2018, 03:31 PM
#12
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I’d venture to guess that either your cam is installed incorrectly, or your pushrods are too long. Basically your valve events are out of sync. Either one of these issues would cause low to no compression however. I’ve seen the backfiring through intake before, and it was caused by too long of a pushrod.
11-05-2018, 01:57 PM
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Just to follow up, truck runs now.
Cam was installed incorrectly. Dot on crank sprocket was off a few teeth. Set TDC and pulled the timing cover off, instantly could tell the cam was off. That's on me for not verifying it was correct during the build
Cam was installed incorrectly. Dot on crank sprocket was off a few teeth. Set TDC and pulled the timing cover off, instantly could tell the cam was off. That's on me for not verifying it was correct during the build
11-05-2018, 02:17 PM
#14
TECH Senior Member
Glad to hear it! I hoped it not only runs, but runs WELL!